1. Field of the Invention
The present invention relates in general to hermetic reciprocating compressors and, more particularly, to a structural improvement in a coupling portion between a piston and a shell of the hermetic reciprocating compressor for preventing abrasion of the piston as well as abrasion of the contact part between a slider and the shell.
2. Description of the Prior Art
As shown in FIGS. 1A to FIG. 1C, the moving part of a typical hermetic reciprocating compressor such as a Scotch yoke compressor comprises a crank shaft part, a slider 2 and a piston part. The crank shaft part includes a cylindrical rotator 6, a crank shaft 7 penetrating the center of the rotator 6, and a counter balance 9 of the hollow tube type mounted on the top of the crank shaft 7. The crank shaft part also includes a crank pin 1 which will be coupled to another crank shaft (not shown). Conventionally, the above elements of the crank shaft part are assembled with each other into the crank shaft part of a single body. The slider 2, which is received in a cylindrical shell 3, has a size of about 1/2 of the shell 3. The piston part comprises a piston 4 and the shell 3.
In operation of the above compressor, the another crank shaft (not shown) is rotated at the same time of the rotation of the rotator 6 of the moving part. At this time, the slider 2 is rotated due to presence of the crank pin 1. That is, when the drive force is transmitted to the slider 2 through the crank pin 1 connected to the another crank shaft, the piston 4 rectilinearly reciprocates in the cylinder 5 because of the sliding motion of both the slider 2 and the shell 3, thus to suck and compress the gas refrigerant.
In operation of the slider crank mechanism or the above moving part of the hermetic reciprocating compressor, the slider 2 repeatedly strikes on the shell 3 when the torque of a motor (not shown) is transmitted to the piston 4 through the slider 2. The contact part between the slider 2 and the shell 3 of the moving part will thus abrade. Furthermore, the mechanical shock generated when the slider 2 strikes on the shell 3 is inevitably applied on the piston 4, thus to cause the side surface of the piston 4 to repeatedly come into contact with the inner surface of the cylinder 5. The side surface of the piston 4 will thus abrade.